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<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
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<body>
    <script>
        //声明变量
        let a;
        let b;
        let c = 123;

        //1.变量不能重复声明
        let star = "测试"

        // let star = "星"//不能重复命名


        // 2.块级作用域
        {
            let a = null
        }

        //3.不存在变量提升

        console.log(lili);
        let lili = "123"
    </script>
</body>

</html>